Vermont Gas can go ahead with the Addison County natural gas pipeline project despite a 40 percent increase in the cost of the project, the Public Service Board ruled.

The board had been reconsidering the project's certificate of public good because the estimated cost of the project jumped from $86 million to $121 million.

Though the three-member board called the cost increase "substantial," it ruled Friday that it wasn't enough to reopen the certificate of public good process for the multi-million dollar project. The board said the new information about cost was not enough to change its decision "that approval of the project ... will promote the general good of Vermont."

Steve Wark, spokesman for Vermont Gas Systems, said "We're very pleased with the decision and we really do look forward to continuing to extend the environmental and economic benefits of natural gas to Vermonters."

Those who argued for reconsidering the project said they were disappointed that the board was unwilling to take more testimony about the impact of the cost increase.

"The board took a very narrow view," said Sandy Levine, senior attorney for Conservation Law Foundation. "It made its decision based on very little evidence."

Levine said appealing the decision is a possibility. Conservation Law Foundation and others also have asked the board to amend the project's certificate of public good, separate from Friday's decision. The board has also yet to rule on whether or how much Vermont Gas will be fined for failing to tell the board in a timely manner about the cost increase.

AARP Vermont criticized the Public Service Department, which is independent of the board, for its continued support of the project despite the cost increase, calling it a failure to represent the consumer.

"The DPS has done a terrific job of actually defending the utility and their pipeline plan instead of representing the ratepayers it is supposed to look out for," AARP Vermont said in a statement.

Opponents of the project, including Rising Ride Vermont, 350 Vermont and the Vermont Workers' Center, plan a protest for 3 p.m. Oct. 27 on the Statehouse lawn in Montpelier.

The project would extend a natural gas pipeline 43 miles from Colchester to Middlebury. The project is already under construction while Vermont Gas continues to negotiate with property owners along the route to acquire land. Vermont Gas also plans to extend the pipeline across Lake Champlain to Ticonderoga, N.Y., and to Rutland. Approval of the Ticonderoga phase is pending approval from the Public Service Board.